An Aquaculture-Based Method for Calibrated Bivalve Isotope Paleothermometry

To quantify species- specific relationships between bivalve carbonate isotope geochemistry ( delta O-18(c)) and water conditions ( temperature and salinity, related to water isotopic composition [delta O-18(w)]), an aquaculture-based methodology was developed and applied to Mytilus edulis ( blue mussel). The four- by- three factorial design consisted of four circulating temperature baths ( 7, 11, 15, and 19 degrees C) and three salinity ranges ( 23, 28, and 32 parts per thousand ( ppt); monitored for delta O-18(w) weekly). In mid- July of 2003, 4800 juvenile mussels were collected in Salt Bay, Damariscotta, Maine, and were placed in each configuration. The size distribution of harvested mussels, based on 105 specimens, ranged from 10.9 mm to 29.5 mm with a mean size of 19.8 mm. The mussels were grown in controlled conditions for up to 8.5 months, and a paleotemperature relationship based on juvenile M. edulis from Maine was developed from animals harvested at months 4, 5, and 8.5. This relationship [ T degrees C = 16.19 (+/- 0.14) - 4.69 (+/- 0.21) {delta O-18(c) VPBD - delta O-18(w) VSMOW} + 0.17 (+/- 0.13) {delta O-18(c) VPBD - delta O-18(w) VSMOW}(2); r(2) = 0.99; N = 105; P < 0.0001] is nearly identical to the Kim and O'Neil ( 1997) abiogenic calcite equation over the entire temperature range ( 7 - 19 degrees C), and it closely resembles the commonly used paleotemperature equations of Epstein et al. ( 1953) and Horibe and Oba ( 1972). Further, the comparison of the M. edulis paleotemperature equation with the Kim and O'Neil ( 1997) equilibrium- based equation indicates that M. edulis specimens used in this study precipitated their shell in isotopic equilibrium with ambient water within the experimental uncertainties of both studies. The aquaculture- based methodology described here allows similar species- specific isotope paleothermometer calibrations to be performed with other bivalve species and thus provides improved quantitative paleoenvironmental reconstructions.

Characterization of HFO2 Capacitors

Hafnium oxide (HfOn) is a promising dielectric for future microelectronic applications. Hf02 thin films (10-75nm) were deposited on Pt/Si02/Si substrates by pulsed DC magnetron reactive sputtering. Top electrodes of Pt were formed by e-beam evapo- ration through an aperture mask on the samples to create MIM (Metal-Insulator-Metal) capacitors. Various processing conditions (Arloz ratio, DC power and deposition rate) and post-deposition annealing conditions (time and temperature) were investigated. The structure of the Hf02 films was characterized by X-ray diffraction (XRD) and the roughness was measured by a profilometer. The electrical properties were characterized in terms of their relative permittivity (E,(T) and ~,.(f)) and leakage behavior (I-V, I-T and I- time). The electrical measurements were performed over a temperature range from -5 to 200°C. For the samples with best experimental results, the relative permittivity of HfOa was found to be -- 27 after anneal and increased by 0.027%/"C with increasing temperature over the measured temperature range. At 25"C, leakage current density was below lop8 ~ l c m ' at 1 volt. The leakage current increased with temperature above a specific threshold temperature below which the leakage current didn't change much. The leakage current increased with voltage. At voltages below lvolt, it's ohmic; at higher voltages, it follows Schottky model. The breakdown field is - 1 . 8 2 ~ lo6 Vlcm. The optical bandgap was measured with samples deposited on quartz substrates to be 5.4eV after anneal.